Information transfer method radio terminal and radio gateway device using datalink layer signaling of protocol identifier

ABSTRACT

A radio terminal or gateway capable of executing the AV/C protocol on the datalink protocol which starts communications after setting up a logical channel on a radio network is disclosed. The radio terminal or gateway transfers data packets according to the stored correspondence information among the protocol identifier, the channel identifier that is set up for the radio terminal or gateway, and the channel identifier that is set up for a correspondent radio terminal or gateway, where the correspondence information is obtained through an exchange of signaling packets containing the channel identifier indicating a logical channel that is set up for transferring the data packets and the protocol identifier indicating the AV control protocol.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a radio terminal belonging to aradio network for carrying out communications by setting up logicalchannels on a radio network in advance and an information transfermethod of a radio terminal, as well as to a radio gateway device forconnecting an IEEE 1394 bus with a radio network for carrying outcommunications by setting up logical channels on a radio network inadvance and an information transfer method of a radio gateway device.

[0003] 2. Description of the Background Art

[0004] In recent years, the realization of home network is attractingmuch attention, and in particular, the IEEE 1394 bus for connectingbetween digital home electronic devices has been attracting considerableattention. The IEEE 1394 bus is capable of connecting a plurality ofIEEE nodes in daisy chain or star connection and transferring a widebanddata in excess of 100 Mbps. Also, it has a major feature that it ispossible to transmit both asynchronous data and isochronous data on thesame cable. For this reason, even though the IEEE 1394 bus wasoriginally developed as a next generation version of SCSI, there areincreasing trends to use the IEEE 1394 bus as a cable for connecting AVdevices.

[0005] On the other hand, the realization of fast radio network (radioLAN) is also attracting attention. In particular, since thedetermination of the IEEE 802.11 specification in 1998, many radio LANproducts are appearing in the market and there has been a remarkabledecrease in the prices of these radio LAN products.

[0006] In conjunction with this trend for improved performance andreduced cost of the radio technology, there is an active trend toconsider applications of the radio technology to the home environmentand this trend is expected to grow further in future as can beanticipated by establishment of organizations of related companies suchas HomeRF and Bluetooth (a kind of radio system using 2.4 GHz band) inthe U.S.A. Also, from a viewpoint of the home network, the radio systemis an easily acceptable system as it does not require any new cableconstruction. For this reason, a network system merging the IEEE 1394bus and the fast and inexpensive radio LAN system is expected to play acentral role in the future home network.

[0007] In such an environment for merging the IEEE 1394 bus and theradio network, there are several outstanding problems.

[0008] For example, one of the problems is how a protocol executed onthe IEEE 1394 bus (a protocol presupposing the IEEE 1394 at the datalinklayer such as AV/C protocol) can be executed over the radio network. Inparticular, in the case of executing a protocol such as the AV/Cprotocol in which message types (command, response, etc.) on theprotocol are identified by logical addresses (registers) on the IEEE1394 bus (where a value indicating an AV/C command or a value indicatingan AV/C response can be found by reading a register according to anoffset value described in a packet), identifiers corresponding to thelogical addresses on that IEEE 1394 bus must also be provided at theradio LAN side. This situation is similar in the case of executing theAV/C protocol or the like between radio terminals.

SUMMARY OF THE INVENTION

[0009] It is therefore an object of the present invention to provide aradio terminal and its information transfer method which are capable ofexecuting the AV control protocol by expanding it over to a radionetwork for executing data transfer after establishing a logicalconnection between radio terminals prior to data transfer between radioterminals.

[0010] It is another object of the present invention to provide a radiogateway device and its information transfer method which are capable ofexecuting the AV control protocol by expanding it over to a radionetwork at a radio gateway for connecting the IEEE 1394 bus with a radionetwork for executing data transfer after establishing a logicalconnection between radio terminals prior to data transfer between radioterminals.

[0011] According to one aspect of the present invention there isprovided an information transfer method for transferring informationregarding an AV control protocol in a radio system for carrying out datatransfer after establishing a logical connection between radio terminalsor gateways prior to data transfer between radio terminals or gateways,the method comprising the steps of: exchanging signaling packets forsignaling at a datalink layer between the radio terminals or gatewaysprior to an exchange of data packets on which the information regardingthe AV control protocol is loaded, each signaling packet containing achannel identifier indicating a logical channel that is set up fortransferring the data packets and a protocol identifier indicating theAV control protocol, such that a signaling packet transmitted from eachradio terminal or gateway indicates a channel identifier that is set upfor the each radio terminal or gateway and a signaling packet receivedfrom a correspondent radio terminal or gateway indicates a channelidentifier that is set up for the correspondent radio terminal orgateway; storing at the each radio terminal or gateway a correspondenceinformation obtained through an exchange of the signaling packets, thecorrespondence information indicating a correspondence among theprotocol identifier, the channel identifier that is set up for the eachradio terminal or gateway, and the channel identifier that is set up forthe correspondent radio terminal or gateway; and transferring the datapackets between the radio terminals or gateways, according to thecorrespondence information.

[0012] According to another aspect of the present invention there isprovided an information transfer method for transferring informationregarding an AV control protocol at a radio gateway connecting an IEEE1394 bus with a radio network for carrying out data transfer afterestablishing a logical connection between radio terminals or gatewaysprior to data transfer between radio terminals or gateways, the methodcomprising the steps of: exchanging signaling packets for signaling at adatalink layer with a correspondent radio terminal or gateway on theradio network prior to an exchange of data packets on which theinformation regarding the AV control protocol is loaded, each signalingpacket containing a channel identifier indicating a logical channel thatis set up for transferring the data packets and a protocol identifierindicating the AV control protocol, such that a signaling packettransmitted from the radio gateway indicates a channel identifier thatis set up for the radio gateway and a signaling packet received from thecorrespondent radio terminal or gateway indicates a channel identifierthat is set up for the correspondent radio terminal or gateway; storinga correspondence information obtained through an exchange of thesignaling packets, the correspondence information indicating acorrespondence among the protocol identifier, the channel identifierthat is set up for the radio gateway, and the channel identifier that isset up for the correspondent radio terminal or gateway; and transferringthe data packets from a radio network side to an IEEE 1394 bus side orfrom the IEEE 1394 bus side to the radio network side, according to thecorrespondence information.

[0013] According to another aspect of the present invention there isprovided a radio terminal device in a radio system for carrying out datatransfer after establishing a logical connection between radio terminalsor gateways prior to data transfer between radio terminals or gateways,the radio terminal device comprising: a signaling packet exchange unitconfigured to exchange signaling packets for signaling at a datalinklayer with a correspondent radio terminal or gateway prior to anexchange of data packets on which the information regarding the AVcontrol protocol is loaded, each signaling packet containing a channelidentifier indicating a logical channel that is set up for transferringthe data packets and a protocol identifier indicating the AV controlprotocol, such that a signaling packet transmitted from the radioterminal device indicates a channel identifier that is set up for theradio terminal device and a signaling packet received from thecorrespondent radio terminal or gateway indicates a channel identifierthat is set up for the correspondent radio terminal or gateway; a memoryunit configured to store a correspondence information obtained throughan exchange of the signaling packets, the correspondence informationindicating a correspondence among the protocol identifier, the channelidentifier that is set up for the radio terminal device, and the channelidentifier that is set up for the correspondent radio terminal orgateway; and a data packet exchange unit configured to exchange the datapackets with the correspondent radio terminal or gateway, according tothe correspondence information.

[0014] According to another aspect of the present invention there isprovided a radio gateway device connecting an IEEE 1394 bus with a radionetwork for carrying out data transfer after establishing a logicalconnection between radio terminals or gateways prior to data transferbetween radio terminals or gateways, the radio gateway devicecomprising: a signaling packet exchange unit configured to exchangesignaling packets for signaling at a datalink layer with a correspondentradio terminal or gateway on the radio network prior to an exchange ofdata packets on which information regarding an AV control protocol isloaded, each signaling packet containing a channel identifier indicatinga logical channel that is set up for transferring the data packets and aprotocol identifier indicating the AV control protocol, such that asignaling packet transmitted from the radio gateway device indicates achannel identifier that is set up for the radio gateway device and asignaling packet received from the correspondent radio terminal orgateway indicates a channel identifier that is set up for thecorrespondent radio terminal or gateway; a memory unit configured tostore a correspondence information obtained through an exchange of thesignaling packets, the correspondence information indicating acorrespondence among the protocol identifier, the channel identifierthat is set up for the radio gateway device, and the channel identifierthat is set up for the correspondent radio terminal or gateway; and adata packet transfer unit configured to transfer the data packets from aradio network side to an IEEE 1394 bus side or from the IEEE 1394 busside to the radio network side, according to the correspondenceinformation.

[0015] According to another aspect of the present invention there isprovided a computer usable medium having computer readable program codesembodied therein for causing a computer to function as a radio terminaldevice in a radio system for carrying out data transfer afterestablishing a logical connection between radio terminals or gatewaysprior to data transfer between radio terminals or gateways, the computerreadable program codes include: a first computer readable program codefor causing said computer to exchange signaling packets for signaling ata datalink layer with a correspondent radio terminal or gateway prior toan exchange of data packets on which the information regarding the AVcontrol protocol is loaded, each signaling packet containing a channelidentifier indicating a logical channel that is set up for transferringthe data packets and a protocol identifier indicating the AV controlprotocol, such that a signaling packet transmitted from the radioterminal device indicates a channel identifier that is set up for theradio terminal device and a signaling packet received from thecorrespondent radio terminal or gateway indicates a channel identifierthat is set up for the correspondent radio terminal or gateway; a secondcomputer readable program code for causing said computer to store acorrespondence information obtained through an exchange of the signalingpackets, the correspondence information indicating a correspondenceamong the protocol identifier, the channel identifier that is set up forthe radio terminal device, and the channel identifier that is set up forthe correspondent radio terminal or gateway; and a third computerreadable program code for causing said computer to exchange the datapackets with the correspondent radio terminal or gateway, according tothe correspondence information.

[0016] According to another aspect of the present invention there isprovided a computer usable medium having computer readable program codesembodied therein for causing a computer to function as a radio gatewaydevice connecting an IEEE 1394 bus with a radio network for carrying outdata transfer after establishing a logical connection between radioterminals or gateways prior to data transfer between radio terminals orgateways, the computer readable program codes include: a first computerreadable program code for causing said computer to exchange signalingpackets at a datalink layer with a correspondent radio terminal orgateway on the radio network prior to an exchange of data packets onwhich information regarding an AV control protocol is loaded, eachsignaling packet containing a channel identifier indicating a logicalchannel that is set up for transferring the data packets and a protocolidentifier indicating the AV control protocol, such that a signalingpacket transmitted from the radio gateway device indicates a channelidentifier that is set up for the radio gateway device and a signalingpacket received from the correspondent radio terminal or gatewayindicates a channel identifier that is set up for the correspondentradio terminal or gateway; a second computer readable program code forcausing said computer to store a correspondence information obtainedthrough an exchange of the signaling packets, the correspondenceinformation indicating a correspondence among the protocol identifier,the channel identifier that is set up for the radio gateway device, andthe channel identifier that is set up for the correspondent radioterminal or gateway; and a third computer readable program code forcausing said computer to transfer the data packets from a radio networkside to an IEEE 1394 bus side or from the IEEE 1394 bus side to theradio network side, according to the correspondence information.

[0017] Other features and advantages of the present invention willbecome apparent from the following description taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a schematic diagram showing an exemplary radio networkaccording to the first embodiment of the present invention.

[0019]FIG. 2 is a sequence chart for a processing of a packet transferbetween radio terminals in the radio network of FIG. 1.

[0020]FIG. 3 is a diagram showing exemplary correspondence tables to beused in the packet transfer between radio terminals in the radio networkof FIG. 1.

[0021]FIG. 4 is a diagram showing exemplary packet formats for asignaling request packet and a signaling response packet to betransferred between radio terminals in the radio network of FIG. 1.

[0022]FIG. 5 is a diagram showing an exemplary packet format of a datapacket to be transferred between radio terminals in the radio network ofFIG. 1.

[0023]FIG. 6 is a diagram showing an exemplary protocol stack to beexecuted by a radio terminal according to the first embodiment of thepresent invention.

[0024]FIG. 7 is a schematic diagram showing an exemplary radio networkfor executing the AV/C protocol between radio terminals according to thefirst embodiment of the present invention.

[0025]FIG. 8 is a sequence chart for one exemplary processing of AV/Cprotocol execution in the radio network of FIG. 7.

[0026]FIG. 9 is a diagram showing exemplary correspondence tables to beused in the AV/C protocol execution in the radio network of FIG. 7.

[0027]FIG. 10 is a sequence chart for another exemplary processing ofAV/C protocol execution in the radio network of FIG. 7.

[0028]FIG. 11 is a schematic diagram showing an exemplary radio networkfor executing the AV/C protocol between a radio terminal and an IEEE1394 node via a radio gateway according to the second embodiment of thepresent invention.

[0029]FIG. 12 is a sequence chart for one exemplary processing of AV/Cprotocol execution in the radio network of FIG. 11.

[0030]FIG. 13 is a diagram showing exemplary correspondence tables to beused in the AV/C protocol execution in the radio network of FIG. 11.

[0031]FIG. 14 is a sequence chart for another exemplary processing ofAV/C protocol execution in the radio network of FIG. 11.

[0032]FIG. 15 is a block diagram showing an exemplary configuration of aradio terminal device according to the present invention.

[0033]FIG. 16 is a block diagram showing an exemplary configuration of aradio gateway device according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] First, the main features of the present invention will besummarized briefly.

[0035] In the present invention, the protocol identifier of the AVcontrol protocol is defined as a protocol identifier of a datalink layerpacket in a radio system for executing data transfer after establishinga logical connection between radio terminals prior to data transferbetween radio terminals. For example, the AV/C protocol is added as aprotocol identifier of an L2CAP packet in the Bluetooth. In this case,the AV control protocol can be identified from the protocol identifierat the datalink layer (a message type in this AV control protocol can beidentified from at an upper layer protocol).

[0036] Alternatively, the protocol identifier of the AV control protocolis defined as a protocol identifier of a datalink layer packet, for eachmessage type separately. For example, the AV/C command of the AV/C andthe AV/C response of the AV/C protocol are added as protocol identifiersof an L2CAP packet in the Bluetooth. In this case, the AV controlprotocol as well as the message type in this AV control protocol can beidentified from the protocol identifier at the datalink layer.

[0037] Also, datalink layer signaling packet are exchanged between radioterminals, where the datalink layer signaling packet contains a channelidentifier indicating a logical channel that is set up for the purposeof transferring a packet on which information regarding this AV controlprotocol is loaded and a protocol identifier indicating this AV controlprotocol, and each radio terminal stores a correspondence informationamong the protocol identifier, a channel identifier of a channel that isset up for the own terminal, and the a channel identifier of a channelthat is set up for a correspondent radio terminal, which are obtainedthrough the signaling packet exchange. Thereafter, the data packet onwhich information regarding this AV control protocol is loaded will betransferred by attaching the correspondent channel identifier, such thatthe receiving side can judge that the received packet is a packetregarding the AV control protocol, from the channel identifier attachedto the received packet, at the datalink layer.

[0038] Also, in the present invention, the protocol identifier of the AVcontrol protocol is defined as a protocol identifier of a datalink layerpacket with respect to a radio network side, similarly as describedabove, at a radio gateway device for connecting the IEEE 1394 bus with aradio network for carrying out data transfer after establishing alogical connection between radio terminals prior to data transferbetween radio terminals (such that the AV control protocol can beidentified from a protocol identifier at a datalink layer). Also, anaccess (read/write) with respect to a specific register on the IEEE 1394bus can be set in correspondence with a protocol identifier on the radionetwork (in the case of the AV/C protocol, a register offset value foran AV/C command and a register offset value for an AV/C response can beset in correspondence with the same protocol identifier).

[0039] Alternatively, similarly as described above, the protocolidentifier of the AV control protocol is defined as a protocolidentifier of a datalink layer packet, for each message type separately,with respect to a radio network side (such that the AV control protocolas well the message type in this AV control protocol can be identifiedfrom the protocol identifier at the datalink layer). Also, an access(read/write) with respect to a specific register on the IEEE 1394 buscan be set in correspondence with a protocol identifier on the radionetwork (in the case of the AV/C protocol, a register offset value foran AV/C command can be set in correspondence to a protocol identifier ofthe AV/C command, and a register offset value for an AV/C response canbe set in correspondence with a protocol identifier of the AV/Cresponse).

[0040] A radio network section between the radio gateway device and theradio terminal is the same as between radio terminals described above.Also, in the packet relay processing between the radio network and theIEEE 1394 bus at the radio gateway device, a correspondence informationis set up in advance by carrying out the signaling with the radioterminal as described above, and at a time of transferring a packet fromthe radio network side to the IEEE 1394 bus side, the fact that it is anAV/C command or an AV/C response of the AV/C protocol is ascertainedfrom the channel identifier (or the channel identifier and the upperlayer processing) in the received packet, and a packet is transferred tothe IEEE 1394 side by describing a corresponding register offset valuetherein. Also, at a time of transferring a packet from the IEEE 1394 busside to the radio network side, the fact that it is an AV/C command oran AV/C response of the AV/C protocol is ascertained from the registeroffset value, and a packet is transferred to the radio network side bydescribing a correspondent channel identifier therein.

[0041] According to the present invention, even in the case of using aradio LAN system for carrying out data transfer after establishing alogical connection between radio terminals prior to data transferbetween radio terminals, it is possible to execute a protocol such asAV/C protocol for which the protocol processing is to be carried out byusing a combination of a command and a response as one set. Also, byassigning a channel identifier corresponding to a protocol to beexecuted in advance, it is possible to simplify the datalink layerprocessing on the radio terminal.

[0042] Also, according to the present invention, it is possible toexecute the AV/C protocol on the datalink protocol which startscommunications after setting up a logical channel on a radio network. Itis also possible to execute the AV/C protocol across such a radionetwork and the IEEE 1394 bus. In particular, it is possible to realizethe AV data transfer control processing across the IEEE 1394 and theBluetooth which is a kind of radio system using 2.4 GHz band.

[0043] Thus, according to the present invention, it is possible tocontrol a protocol that presupposes the IEEE 1394 such as AV/C protocolacross the radio network and the IEEE 1394 bus.

FIRST EMBODIMENT

[0044] Referring now to FIG. 1 to FIG. 10, the first embodiment of thepresent invention will be described in detail.

[0045] The first embodiment is directed to the case where a radio LANsystem is assumed to be a system for carrying out data transfer afterestablishing a logical connection between radio terminals prior to datatransfer between radio terminals. For example, the Bluetooth can be usedas such a radio LAN system.

[0046]FIG. 1 shows an exemplary basic configuration of a radio networkin the first embodiment, and FIG. 2 shows an exemplary basic processingsequence in the case of carrying out packet transfer between radioterminals in the first embodiment. In the radio LAN system shown in FIG.1, at a time of transferring data related to some protocol P between tworadio terminals 901 and 902 that are connected to a radio network 90through radio interfaces 9013 and 9023, the processing shown in FIG. 2will be carried out. Note that, in FIG. 1, it is assumed that the radioterminal 901 has a node ID=[X] and the radio terminal 902 has a nodeID=[Y].

[0047] The processing sequence of FIG. 2 is carried out as follows.

[0048] (1: Signaling processing)

[0049] First, prior to data transfer by the protocol P between the radioterminal 901 and the radio terminal 902, the signaling processing iscarried out between the radio terminals 901 and 902, such that a channelidentifier (abbreviated hereafter as channel ID) regarding a logicalconnection is acquired at a datalink layer in each one of the radioterminals 901 and 902 (here it is assumed that channel IDs A and B arerespectively acquired in this example). Note that the acquired channelID information is exchanged between the radio terminals by the signalingprocessing.

[0050] (2: Data transfer processing)

[0051] Next, the data transfer between the radio terminal 901 and theradio terminal 902 is carried out through the logical connectionidentified by the channel IDs (A, B) at the datalink layer in the radioterminals 901 and 902 that are established by the signaling processing(here it is assumed that the channel ID=B on the radio terminal 902 sidewill be used for the data transfer from the radio terminal 901 to theradio terminal 902, and the channel ID =A on the radio terminal 901 sidewill be used for the data transfer from the radio terminal 902 to theradio terminal 901 in this example).

[0052] (3: Channel release processing)

[0053] After that, when a prescribed condition is satisfied, thislogical connection is disconnected, and the channel IDs (A, B) that havebeen acquired at the datalink layer in the radio terminals 901 and 902will be released. The prescribed condition can be satisfied when it isrequested from the radio terminal 901 as indicated in FIG. 2, or when aprescribed period of time has elapsed since that channel ID is acquired,or when a prescribed period of time has elapsed since the datacommunication related to that channel ID was carried out last, forexample. The channel can also be disconnected when the power of theradio terminal is turned off, or when the battery remaining powerbecomes less than a prescribed threshold, for example (in other words,the channel may not be disconnected until the power is turned off, forexample).

[0054] A part (a) of FIG. 3 shows an example of a correspondence table#1 to be created at the radio terminal 901 and a part (b) of FIG. 3shows an example of a correspondence table #2 to be created at the radioterminal 902, in the signaling processing of the processing sequence ofFIG. 2.

[0055] Each correspondence table has a format in which a protocol, achannel ID of the own terminal (own channel ID) for executing thatprotocol, a node ID of a correspondent terminal (correspondent node ID),and a channel ID of that correspondent terminal (correspondent channelID) are stored in correspondence.

[0056] As a specific example in accordance with FIG. 1, thecorrespondence table #1 in the radio terminal 901 shown in a part (a) ofFIG. 3 records a correspondence among the protocol=“P”, the own channelID=“A”, the correspondent node ID=“Y” (=the node ID of the radioterminal 902), and the correspondent channel ID=“B”. Similarly, thecorrespondence table #2 in the radio terminal 902 shown in a part (b) ofFIG. 3 records a correspondence among the protocol=“P”, the own channelID=“B”, the correspondent node ID=“X” (=the node ID of the radioterminal 901) and the correspondent channel ID=“A”.

[0057] A part (a) of FIG. 4 shows an exemplary packet format for asignaling request packet and a part (b) of FIG. 4 shows an exemplarypacket format for a signaling response packet, which are to be used inthe signaling processing in this radio LAN system.

[0058] In the example shown in FIG. 4, the signaling information to betransferred contains the own channel ID (in the case of the signalingrequest packet) or the own channel ID and the correspondent channel ID(in the case of the signaling response packet) as well as the protocolID of a protocol to be executed from now on.

[0059] In this way, each one of the radio terminals 901 and 902 canmaintain a correspondence between a newly acquired channel ID at thedatalink layer and the upper layer protocol to be executed on the ownterminal (by using that channel ID).

[0060] As the correspondence between the channel ID of the own terminaland the upper layer protocol can be maintained by the signalingprocessing, a packet to be used for the actual data transfer will not beattached with the upper layer protocol and it suffices to attach a valueof the corresponding channel ID as shown in FIG. 5. Namely, the radioterminal on the transmitting side will transfer the packet by referringto the correspondence table in the own terminal and attaching a value ofthe channel ID on the correspondent terminal to which that upper layerprotocol packet is to be transmitted (that is, the correspondent channelID of the correspondence table shown in FIG. 3) to a header portion.Then, the radio terminal on the receiving side can ascertain even theupper layer protocol by referring to the correspondence table in the ownterminal by using the channel ID attached to the packet as the ownchannel ID.

[0061] In this way, it is possible to improve the data transferefficiency in the actual data transfer.

[0062] In the following, the case where the AV control protocol asdefined by the IEEE 1394 is to be executed between radio terminals inthe radio LAN system as described above, and the case where the AVcontrol protocol is to be executed between a radio terminal on the radioLAN system as described above and a 1394 node on the IEEE 1394 bus willbe described in detail.

[0063]FIG. 6 shows an exemplary protocol stack for the AV data transferscheme to be executed by the radio terminals in the followingdescription.

[0064] The protocol stack of FIG. 6 is for the case of using theBluetooth (in which a physical layer is Baseband and a datalink layer isL2CAP), that is currently under the process of standardization, as theradio system.

[0065] The protocol stack of FIG. 6 is also for the case of executingthe AV/C protocol as defined by the IEEE 1394 as the AV control protocolfor transferring AV data and thereby providing a function such as the socalled session control processing, at a time of executing an AVapplication at the radio terminal.

[0066] Note that the AV/C protocol recognizes nodes in terms of Units,and constituent elements (such as Display or VTR, for example) withineach node in terms of SubUnits. Also, in the protocol for transferringthe AV/C control commands (commands such as “play”, “stop”, “fastforward”, etc.), a transmission of a command and a reception of aresponse are to be carried out as one set.

[0067] In addition, in the protocol stack of FIG. 6, a group ofprotocols related to the actual AV data transfer are used (a block 4 ofFIG. 6). For example, various data such as video data, audio data andinformation data can be transferred by respective RTP (RealtimeTransport Protocol) packets, the RTP packets can be further encapsulatedinto L2CAP packets according to the datalink layer protocol of theBluetooth, and the AV data transfer control information can be exchangedusing the RTCP protocol (RTP Control Protocol), but the presentinvention is not necessarily limited to this case.

[0068]FIG. 6 shows an internal configuration regarding the protocolprocessing of the radio terminal, which includes processing units forexecuting respective protocols, i.e., a Baseband processing unit 1 forexecuting the physical layer processing of the Bluetooth, an L2CAPprocessing unit 2 for executing the datalink layer processing of theBluetooth, an AV/C protocol processing unit 3 for executing the AV/Cprotocol at an upper layer of the L2CAP processing unit 2, an AV datatransfer processing unit 4 for executing a group of protocols related tothe actual AV data transfer (the AV data transfer processing unit 4 hasRTP processing units 41 for executing the RTP protocol, and a Videoprocessing unit 43, an Audio processing unit 44, and Data processingunit 45 provided at an upper layer of the RTP processing unit 41, and anRTCP processing unit 42 for executing the RTCP protocol, for example),and an AV application processing unit 5 for executing an AV applicationat an upper layer of the AV/C protocol processing unit 3 and the AV datatransfer processing unit 4.

[0069] Note here that, a radio gateway device to be described in thesecond embodiment below will have a physical processing unit and adatalink layer processing unit of the IEEE 1394 bus, and a gatewayfunction processing unit for enabling execution of the AV/C protocolacross the radio network and the IEEE 1394, in addition to theconfiguration shown in FIG. 6. The gateway function processing unitexecutes a Proxy processing of the AV/C protocol, etc.

[0070] Note also that the above description is directed to an exemplarycase of using the RTP protocol and the RTCP protocol as exemplaryprotocols for transferring AV data and their control information, butthe present invention is also applicable to the case of using any otherAV transfer protocol.

[0071] The present invention is also applicable to the case where the AVdata are to be transferred by being multiplexed using H.223 protocol orthe like.

[0072] First, the case of executing the AV control protocol as definedby the IEEE 1394 between radio terminals in the radio LAN system forcarrying out data transfer after establishing a logical connectionbetween radio terminals prior to data transfer between radio terminalswill be described.

[0073] Here, an identifier for the AV/C protocol is defined as one ofprotocol identifiers (PSM (Protocol Service Multiplexor)) on the radioLAN, and the datalink layer protocol on the radio LAN carries out thepacket transfer after setting up a logical connection at the datalinklayer whenever a packet according to the AV/C protocol is to betransmitted. Also, whether it is an AV/C command or an AV/C response isidentified at an upper layer (the AV/C protocol processing unit 3 ofFIG. 6, for example) of the datalink layer rather than at the datalinklayer.

[0074]FIG. 7 shows an exemplary configuration of a radio network in thiscase.

[0075] In FIG. 7, a radio terminal 101 and a radio terminal 102 areconnected to a radio network 10 through radio interfaces 1013 and 1023,and FIG. 7 depicts the case where MPEG4 data in the radio terminal 102are to be playbacked/viewed at the radio terminal 101 through this radionetwork 10.

[0076]FIG. 7 is also directed to the case of executing the AV/C protocolas defined by the IEEE 1394 as the AV control protocol for transmittingcommands for the MPEG4 data transfer between the radio terminal 101 andthe radio terminal 102.

[0077] In the AV/C protocol, functions (such as VTR function or Displayfunction) within each terminal are to be recognized in terms ofSubUnits, and a command is to be transmitted with respect to thisSubUnit. In FIG. 7, a Display SubUnit 1011 as a function forplaybacking/viewing the NPEG4 data is provided at the radio terminal101, while a VTR SubUnit 1021 as a function for transmitting the MPEG4data and a MEPG4 source 1022 as a function for storing the MPEG4 dataare provided at the radio terminal 102 (here it is assumed that theMPEG4 source 1022 is regarded as being contained in the VTR SubUnit 1021on the AV/C protocol).

[0078] In FIG. 7, it is assumed that the radio terminal 101 has a nodeID=[X] and the radio terminal 102 has a node ID=[Y].

[0079]FIG. 8 shows an exemplary procedure for executing the AV/Cprotocol between the radio terminal 101 and the radio terminal 102 inthis case.

[0080] In the AV/C protocol, a transfer of a command information and atransfer of a response information corresponding to that command are tobe executed as one set. Consequently, in this embodiment, one logicalchannel (a channel ID at the datalink layer of each radio terminal) isassigned to each combination of a command and a response (one commandprocessing set) in the case of executing the AV/C protocol between theradio terminal 101 and the radio terminal 102.

[0081] Also, FIG. 7 shows an exemplary case where there are only tworadio terminals in the radio network 10, but in practice other radioterminals may also exist and the AV/C protocol may be executed betweenthese other radio terminals. Consequently, in FIG. 8, the correspondinglogical connection is disconnected immediately when the execution of theone command processing set is finished, such that the AV/C command andresponse to be received at respective radio terminals can easilyidentify the corresponding processing. Note that, as described above,there are various methods for controlling the disconnection of thelogical connection, and it is even possible to use a method for notdisconnecting the channel until the power is turned off.

[0082] In the following, the AV/C protocol processing sequence shown inFIG. 8 will be described.

[0083] (1: Signaling processing) A logical connection is establishedbetween the radio terminal 101 and the radio terminal 102.

[0084] At the radio terminal 101, the AV/C protocol with respect to theradio terminal 102 is activated, and a request for acquiring a logicalconnection for this AV/C command transfer (signaling request) istransferred to the datalink layer processing unit (the L2CAP processingunit 2 of FIG. 6, for example) within the own terminal.

[0085] After a channel (which is assumed to be “A”38 ) is acquiredwithin the radio terminal 101, a request for acquiring a channel of theradio terminal 102 corresponding to the channel “A” is transferred tothe radio terminal 102. A packet to be transferred here contains adescription of a channel ID at the radio terminal 101 [A] and a protocolID of the protocol to be executed [AV/C] entered by the datalink layerprocessing unit (see a part (a) of FIG. 4).

[0086] At the radio terminal 102 which received the above channelacquisition request, when the datalink processing unit recognizes thatthe above protocol ID described in the channel acquisition requestindicates the AV/C protocol, a channel (which is assumed to be “B”) isacquired as a channel for executing the AV/C protocol with the radioterminal 101. Also, this fact (the fact that the channel “A” is acquiredat the radio terminal 101 side and the channel “B” is acquired at theradio terminal 102 side as the logical connection for the AV/C commandtransfer) is notified to the AV/C protocol processing unit (the AV/Cprotocol processing unit 3 of FIG. 6, for example) on the own terminal.

[0087] A channel acquisition response (signaling response) indicatingthat the channel [B] is assigned in response to a request from thechannel [A] on the radio terminal 101 is transmitted from the radioterminal 102 to the radio terminal 101. A packet to be transferred herecontains a description of the channel ID at the radio terminal 101 [A],the corresponding channel ID at the radio terminal 102 [B], and theprotocol ID of the protocol to be executed [AV/C] entered by thedatalink layer processing unit (see a part (b) of FIG. 4). Also, thisfact (the fact that the channel “A” is acquired at the radio terminal101 side and the channel “B” is acquired at the radio terminal 102 sideas the logical connection for the AV/C command transfer) is notified tothe AV/C protocol processing unit.

[0088] Note that, when the channel [B] is acquired, the correspondencetable #2 storing the correspondence of the channels is created at theradio terminal 102 (see a part (b) of FIG. 9).

[0089] At the radio terminal 101 which received the above channelacquisition response, the fact that the channel ID [B] is acquired inthe radio terminal 102 in correspondence to the channel ID [A] acquiredin the own terminal in order to execute the AV/C protocol is recognizedby referring to the above identification information described in thechannel acquisition response.

[0090] Note that, at this point, the correspondence table #1 storing thecorrespondence of the channels is created at the radio terminal 101 (seea part (a) of FIG. 9).

[0091] A part (a) of FIG. 9 shows an example of the correspondence table#1 to be maintained at the radio terminal 101 and a part (b) of FIG. 9shows an example of the correspondence table #2 to be maintained at theradio terminal 102 in the series of processing described above.

[0092] Each correspondence table shown in FIG. 9 registers the AV/Cprotocol as the protocol executed at each radio terminal, and incorrespondence to that, a channel ID at the datalink layer of the ownterminal ([A] in the correspondence table #1, [B] in the correspondencetable #2), a node ID of the correspondent radio terminal which isexecuting this protocol, and a channel ID at the datalink layer of thatcorrespondent radio terminal ([B] in the correspondence table #1, [A] inthe correspondence table #2) are stored. Using such a correspondencetable, it is possible to identify a value of the destination channel IDof a transmission packet in the AV/C response transmission processing ora protocol of a transfer target of a received packet in the receptionprocessing.

[0093] (2: Data transfer processing) An AV/C command is transmitted fromthe radio terminal 101.

[0094] A desired AV/C command is transmitted from the radio terminal 101toward the radio terminal 102. Namely, at the datalink layer processingunit which received the AV/C command from the AV/C protocol processingunit on the own terminal, this AV/C command is transmitted to the radioterminal 102 by attaching the correspondent channel ID (= “B”) obtainedby referring to the above described correspondence table #1 (AV/Ccommand transmission processing). A packet to be transferred at thispoint contains a description of the channel ID on the radio terminal 102[B] as an information on a destination of this packet, but a descriptionof the own channel ID [A] and the protocol ID of the protocol [AV/C] arenot contained (see FIG. 5).

[0095] At the radio terminal 102 which received the above packet (onwhich the AV/C command is loaded), when it is recognized that data inthis packet is related to the AV/C protocol by referring to the abovedescribed correspondence table #2 by using the channel ID (=“B”)described in the packet as the own channel ID, this data (the AV/Ccommand in this case) is given to the AV/C protocol processing unit onthe own terminal and the processing corresponding to this data (AV/Ccommand) is carried out at the AV/C protocol processing unit, and anAV/C response containing a result of the processing which is produced atthe AV/C protocol processing unit is transmitted to the radio terminal101 by attaching the correspondent channel ID (= “A”) obtained byreferring to the above described correspondence table #2 (AV/C responsetransmission processing). A packet to be transferred at this pointcontains a description of the channel ID on the radio terminal 101 [A]as an information on a destination of this packet (but a description ofthe own channel ID [B] and the protocol ID of the protocol [AV/C] arenot contained).

[0096] Similarly, at the radio terminal 101 which received the abovepacket (on which the AV/C command is loaded), when it is recognized thatdata in this packet is related to the AV/C protocol by referring to theabove described correspondence table #1 by using the channel ID (=“A”)described in the packet as the own channel ID, this data (the AV/Cresponse in this case) is given to the AV/C protocol processing unit onthe own terminal (and the necessary processing is carried out at theAV/C protocol processing unit).

[0097] (3: Channel release processing) The radio terminal 101 whichreceived the AV/C response as described above recognizes that the seriesof AV/C command transfer processing is finished, and requests adisconnection of the logical connection utilized.

[0098] The radio terminal 101 disconnects the channel “A” in the ownterminal, and a request for disconnecting the channel “B” in the radioterminal 102 corresponding to the channel “A” is transmitted to theradio terminal 102.

[0099] The radio terminal 102 disconnects the channel “B” in the ownterminal, and transmits a disconnection processing confirmation messageto the radio terminal 101.

[0100] Note that, in this example, the portion related to the AV/Cprotocol on the correspondence table in each of the radio terminals 101and 102 is deleted when the processing for transferring the AV/C commandand the AV/C response is finished and the channel on the datalink layerof each radio terminal is disconnected (of course, various methods arepossible here as described above).

[0101] Thereafter, the exchange of one set of an AV/C command and anAV/C response as described above is carried out according to the need.

[0102] Note that, when a playback request command (Play command) istransmitted and received as the above described AV/C command, forexample, the AV data transfer by the RTP protocol or the like will becarried out.

[0103] It is also possible to use a method in which the channel ID forthe AV/C protocol is assigned in advance, instead of acquiring thechannel at a time of the individual AV/C command transmission processingas shown in FIG. 8.

[0104]FIG. 10 shows an exemplary AV/C command transfer processingsequence in this case.

[0105] In FIG. 10, the channel (which is assumed to be “A”) for the AV/Cprotocol is assigned in advance at the radio terminal 101 and the radioterminal 102, and data for which a transmission request is made from theAV/C protocol processing unit (the AV/C protocol processing unit 3 ofFIG. 6, for example) on each radio terminal will be always transmittedwith a description of [A] as a value of its transfer target channel ID.Also, when a packet of the channel [A] is received at each radioterminal, data in this received packet will be always transferred to theAV/C protocol processing unit at the upper layer. By assigning thechannel ID for the AV/C protocol in advance in this way, the datalinklayer processing can be simplified. However, in this case, the AV/Cprotocol processing unit on each radio terminal should carry out aprocessing for identifying an AV/C command transmitted by the ownterminal which corresponds to the received AV/C response.

[0106] As described, according to the first embodiment, even in the caseof using a radio LAN system for carrying out data transfer afterestablishing a logical connection between radio terminals prior to datatransfer between radio terminals, it is possible to execute a protocolsuch as AV/C protocol for which the protocol processing is to be carriedout by using a combination of a command and a response as one set. Also,by assigning a channel ID corresponding to a protocol to be executed inadvance, it is possible to simplify the datalink layer processing on theradio terminal.

SECOND EMBODIMENT

[0107] Referring now to FIG. 11 to FIG. 14, the second embodiment of thepresent invention will be described in detail.

[0108] The second embodiment is directed to the case where the AVcontrol protocol is to be executed between a radio terminal on the radioLAN system as described above and a 1394 node on the IEEE 1394 bus, in asystem merging the IEEE 1394 bus with the radio LAN system for carryingout data transfer after establishing a logical connection between radioterminals prior to data transfer between radio terminals.

[0109] Here, again, an identifier for the AV/C protocol is defined asone of protocol identifiers (PSM (Protocol Service Multiplexor)) on theradio LAN, and the datalink layer protocol on the radio LAN carries outthe packet transfer after setting up a logical connection at thedatalink layer whenever a packet according to the AV/C protocol is to betransmitted. Also, whether it is an AV/C command or an AV/C response isidentified at an upper layer (the AV/C protocol processing unit 3 ofFIG. 6, for example) of the datalink layer rather than at the datalinklayer.

[0110]FIG. 11 shows an exemplary configuration of a radio network inthis case.

[0111] In FIG. 11, a radio network 30 similar to that of FIG. 7 and anIEEE 1394 bus 20 are connected by a radio gateway 202, and a 1394 node201 and a radio terminal 203 are provided on the IEEE 1394 bus 20 andthe radio network 30 respectively (the radio terminal 203 and the radiogateway 202 are connected to the radio network 30 through radiointerfaces 2022 and 2032, while the radio gateway 202 and the 1394 node201 are connected to the IEEE 1394 bus 20). FIG. 11 depicts the casewhere MPEG2 data in the 1394 node 201 are to be playbacked/viewed at theradio terminal 203 through the IEEE 1394 bus 20, the radio gateway 202and the radio network 30.

[0112]FIG. 11 is also directed to the case of executing the AV/Cprotocol as defined by the IEEE 1394 as the AV control protocol fortransmitting commands for the MPEG2 data transfer between the radioterminal 203 and the 1394 node 201.

[0113] In FIG. 11, a Display SubUnit 2031 as a function forplaybacking/viewing the MPEG2 data is provided at the radio terminal203, while a VTR SubUnit 2011 as a function for transmitting the MPEG2data and an MPEG2 source 2012 as a function for storing the MPEG2 dataare provided at the 1394 node 201 (here it is assumed that the MPEG2source 2012 is regarded as being contained in the VTR SubUnit 2011 onthe AV/C protocol).

[0114] In FIG. 11, it is assumed that the 1394 node 201 and the radiogateway 202 have node IDs (1394 node IDs) [X] and [Y] on the IEEE 1394bus 20 respectively, while the radio gateway 202 and the radio terminal203 have node IDs (terminal IDs) [A] and [B] on the radio network 30respectively.

[0115] Here, the radio gateway 202 that connects the radio network 30and the IEEE 1394 bus 20 is providing the Proxy function for connectingthe radio network 30 and the IEEE 1394 bus 20 at a layer of the AV/Cprotocol. More specifically, (the radio gateway function 2021 of) theradio gateway 202 makes the VTR SubUnit 2011 that actually exists in the1394 node 201 to appear as if it is existing in the radio gateway 202with respect to the radio terminal 203. In other words, the radioterminal 203 recognizes the VTR SubUnit 2011 as existing in the radiogateway 202. By carrying out such a Proxy processing, it becomespossible for the radio terminal 203 to execute the AV/C protocol withthe 1394 bode 201 on the IEEE 1394 bus 20 by simply executing the AV/Cprotocol as defined on the radio network 30, without becoming consciousof the network configuration (the fact that the radio network 30 isactually operating by being connected to the IEEE 1394 bus 20).

[0116] Also, when a packet (which is assumed to be the AV/C command orthe AV/C response) is received from the radio terminal 203, the radiogateway 202 can recognize this packet as a packet according to the AV/Cprotocol at the datalink layer, from the protocol identifier on theradio LAN contained in the header. Then, whether this packet is the AV/Ccommand or the AV/C response can be ascertained at the upper layer. At atime of transmitting this AV/C command or AV/C response to the 1394 node201, a register offset value corresponding to the AV/C command or AV/Cresponse is described in the header of the packet.

[0117] When a packet (which is assumed to be the AV/C command or theAV/C response) is received from the 1394 node 201, the radio gateway 202can recognize this packet as a packet of the AV/C command or the AV/Cresponse according to the AV/C protocol by reading a correspondingportion of the register according to the register offset value in theheader. At a time of transmitting this AV/C command or AV/C response tothe radio terminal 203, the protocol identifier on the radio LAN thatcorresponds to the AV/C protocol is described in the header of thepacket.

[0118] Now, the case where the MPEG2 data existing on the 1394 node 201are to be playbacked/viewed at the radio terminal 203 in theconfiguration as described above will be described.

[0119]FIG. 12 shows an exemplary processing sequence in the case wherethis radio terminal 203 operates as a control node in the AV/C protocolto transmit a command to the 1394 node 201 and request transmission ofthe MPEG2 data on the 1394 node 201.

[0120] Note that, in FIG. 2, a part of the signaling processing betweenthe radio terminal 203 and the radio gateway 202 is omitted but thissignaling processing is similar to the signaling processing between theradio terminal 101 and the radio terminal 102 in FIG. 8. The fact thatthe AV/C command and the AV/C response are to be executed as one set isalso similar to FIG. 8. The disconnection of the logical connection isalso similar to FIG. 8.

[0121] In the processing of FIG. 12, in order to request the MPEG2 datatransfer, the radio terminal 203 first transmits a command(SubUnit_info) for collecting the SubUnit information on the 1394 node201, and then according to a result of that, the radio terminal 203transmits a command (Play) for requesting the data transmission withrespect to the VTR SubUnit 2011 on the 1394 node 201. FIG. 12 shows anexemplary case where, at times of transmitting these two AV/C commands(SubUnit_info, Play), the data transfer is carried out after acquiring alogical channel on the datalink layer at each radio terminal (a channelis disconnected when the AV/C command transmission and the AV/C responsereception are completed).

[0122] Note that the operation of the radio terminal 203 and a format ofthe correspondence table to be created by the radio terminal 203 arebasically similar to those of the radio terminal 101 of the firstembodiment, and the operation of the radio gateway 202 regarding theradio network section is basically similar to that of the radio terminal102 of the first embodiment.

[0123] Also, in this example, the logical channel acquired for thepurpose of the AV/C command transmission is to be disconnected everytime the AV/C command transmission and the AV/C response reception arecompleted (of course, various methods are possible here as describedabove).

[0124] First, the exchange of the AV/C command and the AV/C response forthe purpose of obtaining the SubUnit information is carried out.

[0125] (1) A logical connection between the radio terminal 203 and theradio gateway 202 is established by the method similar to that of FIG.8. Here it is assumed that a channel [B1] is assigned at the radioterminal 203 and a channel [A1] is assigned at the radio gateway 202 asa result of this.

[0126] (2) The radio terminal 203 transmits the SubUnit_info command forcollecting the SubUnit information within the radio gateway 202, to theradio gateway 202. At this point, the logical channel [A1] on the radionetwork acquired by the previous processing is utilized.

[0127] (3) When the radio gateway 202 that received a packet of thisSubUnit_info command recognizes that this packet is related to the AV/Cprotocol from the channel ID [A1] attached to this packet and that it isthe AV/C command at the upper layer, the radio gateway 202 transfers theSubUnit info command to the 1394 node 201 in order to notify not onlythe SubUnit information within the own terminal but also the SubUnitinformation within the 1394 node on the IEEE 1394 bus that is connectedwith the radio gateway 202 (at this point, the register offset value isset to be a value corresponding to the AV/C command and a transaction IDis attached).

[0128] At the radio gateway 202, a relationship between the logicalchannel [A1] on the radio network and the transaction ID (=M in FIG. 12)on the IEEE 1394 bus to which the AV/C command is to be transferred isstored into the correspondence table at a time of transferring the AV/Ccommand to the 1394 node 201 (see a part (a) of FIG. 13).

[0129] The AV/C command is transferred from the radio gateway 202 to the1394 node 201, and a processing corresponding to that is carried out atthe 1394 node 201.

[0130] After the 1394 node 201 carried out the processing correspondingto the transmitted AV/C command (collecting the SubUnit informationwithin the own terminal and creating a packet), the processing result istransferred to the radio gateway 202 as the AV/C response. At thispoint, a value of the transaction ID of the AV/C response on the IEEE1394 bus is M.

[0131] (4) The radio gateway 202 that received a packet of this AV/Cresponse recognizes that this packet is the AV/C response by referringto the register according to the register offset value attached to thispacket, and ascertains that this AV/C response corresponds to the AV/Ccommand (SubUnit_info command) transmitted earlier from the informationof the correspondence table because the transaction ID attached to thispacket is equal to M.

[0132] (5) The radio gateway 202 recognizes that the transfer target ofthis AV/C response is the radio terminal 203 (logical channel [B1]) fromthe information of the correspondence table, and transfers this AV/Cresponse to the radio terminal 203 through that logical channel [B1](which contains the SubUnit information within the own terminal and thecollected SubUnit information within the 1394 node on the IEEE 1394bus).

[0133] (6) When the radio terminal 203 that received a packet of thisAV/C response recognizes that data in this packet is related to the AV/Cprotocol by referring to the correspondence table by using the channelID (=B1) described in the packet as the own channel ID, this data (whichis the AV/C response in this case) is given to the AV/C protocolprocessing unit on the own terminal (the fact that this data is the AV/Cresponse is ascertained at the AV/C protocol processing unit). At theAV/C protocol processing unit, the SubUnit information inside the radiogateway 202 (which actually contains the SubUnit information within the1394 node 201) can be collected according to this AV/C response. At thispoint, the radio terminal 203 disconnects the logical channel [B1]acquired for the purpose of the AV/C command transmission by regardingthat a desired processing is finished for the time being.

[0134] (7) According to a request for disconnecting the logical channel[A1] from the radio terminal 203, the radio gateway 202 disconnects thelogical channel [A1] and deletes the corresponding information from thecorrespondence table.

[0135] This completes the exchange of one set of the AV/C command andthe AV/C response.

[0136] Next, the exchange of the AV/C command the AV/C responseregarding the data transmission request is carried out.

[0137] (8) The radio terminal 203 establishes the logical connectionbetween the radio terminal 203 and the radio gateway 202 by the methodsimilar to that of FIG. 8, prior to transmission of a next AV/C command(Play command, for example). Here it is assumed that a channel [B2] isassigned at the radio terminal 203 and a channel [A2] is assigned at theradio gateway 202 as a result.

[0138] (9) Thereafter the transfer processing for the AV/C command andthe transfer processing for the AV/C response are carried out byreferring to the correspondence table (see a part (b) of FIG. 13) at theradio gateway 202, the transfer processing for the AV/C command (whichis the Play command here) from the radio terminal 203 to the 1394 node201 is carried out, the corresponding processing is carried out at the1394 node 201, a response to the Play command is transferred from the1394 node 201 to the radio terminal 203, and the disconnectionprocessing for the logical channel is carried out, by the method similarto that described above.

[0139] This completes the exchange of a next one set of the AV/C commandand the AV/C response.

[0140] Thereafter, the exchange of one set of an AV/C command and anAV/C response as described above is carried out according to the need.

[0141] Note that, when a playback request command (Play command) istransmitted and received as the above described AV/C command, forexample, the AV data transfer by the RTP protocol or the like will becarried out.

[0142]FIG. 13 shows an example of the correspondence tables to bemaintained at the radio gateway 202 in the series of processingdescribed above, where a part (a) of FIG. 13 shows an example of thecorrespondence table “a” to be used in the processing related to theSubUnit_info command and its response in FIG. 12, and a part (b) of FIG.13 shows an example of the correspondence table “b” to be used in theprocessing related to the Play command and its response in FIG. 12.

[0143] Each correspondence table shown in FIG. 13 registers the AV/Cprotocol as the protocol executed at each radio terminal, and incorrespondence to that, an own radio channel ID indicating a channel IDat the datalink layer of the own terminal ([A1] in the correspondencetable “a”, [A2] in the correspondence table “b”), a correspondentterminal ID (=[B]) indicating a node ID of the correspondent radioterminal (203) which is executing this protocol, and a correspondentradio channel ID indicating a channel ID at the datalink layer of thatcorrespondent radio terminal (203) ([B1] in the correspondence table a[B2] in the correspondence table “b”) are stored. In addition, eachcorrespondence table also registers a value of a transaction ID on theIEEE 1394 bus (“M” in the correspondence table “a”, and “N” in thecorrespondence table “b”), the own 1394 node ID (=[Y]) indicating a nodeID of this radio gateway 202 on the IEEE 1394 bus, and a correspondent1394 node ID (=[X]) indicating a node ID of the correspondent 1394 node(201), for the purpose of transferring these AV/C command and responseon the IEEE 1394 bus.

[0144] Using such correspondence tables, it is possible to carry out thetransmission processing for the AV/C command and the AV/C responseacross the IEEE 1394 bus and the radio network.

[0145] Note that FIG. 13 shows the case where each correspondence tablemaintains parameters as described above, but parameters to be maintainedin the correspondence table may also include a value of SubUnit_ID whichis a transfer target of the AV/C command or a type of the AV/C command.For example, when there is an information with a description that it isa Notify command which is one type of the AV/C command, this informationmay be maintained without deleting it even when a corresponding AV/Cresponse is received, because it can be expected that a responsecorresponding to a subsequent state change of the 1394 node will bereturned.

[0146] Here, similarly as in the case of FIG. 10 with respect to thecase of FIG. 8, it is also possible to use a method in which the logicalchannel ID for the AV/C protocol is assigned in advance, instead ofacquiring the logical channel on the datalink layer at a time of eachAV/C command transmission processing as shown in FIG. 12.

[0147]FIG. 14 shows an exemplary AV/C command transfer processingsequence in this case.

[0148] In FIG. 14, a logical channel [B1] on the radio terminal 203 anda logical channel [A1] on the radio gateway 202 are assigned in advance,as logical channels for executing the AV/C protocol, between the radioterminal 203 and the radio gateway 202, and the AV/C command for which arequest for transmission to the radio gateway 202 is made from the AV/Cprotocol processing unit (the AV/C protocol processing unit 3 of FIG. 6,for example) on the radio terminal 203 will be always transmitted with adescription of [A1] as a value of its transfer target logical channelID. Also, the AV/C response will be always transmitted with adescription of [B1] as a value of its transfer target logical channelID. Also, when a packet of the logical channel [A1] is received at theradio gateway 202, data in this received packet will be alwaystransferred to the AV/C protocol processing unit at the upper layer, orto a processing unit for transfer to the 1394 node on the IEEE 1394 bus.

[0149] By assigning the logical channel ID for the AV/C protocol inadvance in this way, the datalink layer processing can be simplified.

[0150] Note that the exemplary network configuration of FIG. 11 isdirected to the exemplary case where the radio terminal is a datareceiving side and the 1394 node is a data transmitting side, but thecase where the radio terminal is a transmitting side and the 1394 nodeis a receiving side is also possible similarly.

[0151] Also, the exemplary network configuration of FIG. 11 is directedto the exemplary case where there is only one radio gateway, but thecase of carrying out data transfer between a first 1394 node connectedto a first radio gateway via a first IEEE 1394 bus and a second 1394node connected to a second radio gateway via a second IEEE 1394 bus isalso possible similarly. Also, the case of carrying out data transferbetween a first radio terminal connected to a first radio gateway viaradio and a second radio terminal connected to a second radio gatewayvia radio where the first radio gateway and the second radio gateway areconnected via an IEEE 1394 bus is also possible similarly.

[0152] Now, the AV/C protocol on the IEEE 1394 bus requires adescription of a register offset value in the packet header in order toidentify the AV/C protocol (in practice, different offset values areused for the AV/C command and the AV/C response). In contrast, in thefirst and second embodiments described above, in order to identify theAV/C protocol in a radio LAN system for carrying out data transfer afterestablishing a logical connection between radio terminals prior to datatransfer between radio terminal, a protocol identifier on the radio LANwhich indicates the AV/C protocol is defined and this protocolidentifier indicating the AV/C protocol is to be described in the packetheader at a time of transmitting a packet according to the AV/Cprotocol, and a command and a response are distinguished at the upperlayer. However, it is also possible to distinguish a command and aresponse at the radio datalink layer as well.

[0153] To this end, it suffices to separately define a protocolidentifier indicating the AV/C command and a protocol identifierindicating the AV/C response as protocol identifiers on the radio LAN.In this case, different logical connections, i.e., different channelidentifiers, will be used for the AV/C command and the AV/C response.

[0154] Moreover, it is also possible to separately define protocolidentifiers for the AV/C command in a direction from the first radioterminal to the second radio terminal, the AV/C response in a directionfrom the first radio terminal to the second radio terminal, the AV/Ccommand in a direction from the second radio terminal to the first radioterminal, and the AV/C response in a direction from the second radioterminal to the first radio terminal, as protocol identifiers on theradio LAN. In this case, different logical connections, i.e., differentchannel identifiers, will be used for these four types of the protocolidentifiers.

[0155] As described, according to the first and second embodiments, evenin the case of using a radio LAN system for carrying out data transferafter establishing a logical connection between radio terminals prior todata transfer between radio terminals, it is possible to execute aprotocol such as AV/C protocol for which the protocol processing is tobe carried out by using a combination of a command and a response as oneset. Also, by assigning a channel ID corresponding to a protocol to beexecuted in advance, it is possible to simplify the datalink layerprocessing on the radio terminal.

[0156] Also, according to the first and second embodiments, it becomespossible to realize the AV data transfer control processing across theradio network as described above and control a protocol that presupposesthe IEEE 1394 such as AV/C protocol across the radio network and theIEEE 1394 bus.

[0157] It is to be noted that, in each embodiment described above, thechannel identifier for the AV/C protocol (or for each one of the AV/Ccommand and the AV/C response) is acquired (set up) at a time ofsignaling in the radio system, but it is also possible to acquire one ora plurality of channel identifiers in advance for the AV/C protocol (orfor each one of the AV/C command and the AV/C response) (in the casewhere a plurality of channel identifiers are acquired, the radioterminal can suitably select and use a channel identifier that isavailable at that moment).

[0158] Also, in the above described embodiments, the channel identifierfor the AV/C protocol (or for each one of the AV/C command and the AV/Cresponse) is appropriately assigned at each radio terminal, but it isalso possible to define a plurality of channel identifiers available forthe AV/C protocol (or for each one of the AV/C command and the AV/Cresponse) with respect to all terminals (in which case the radioterminal can suitably select and use a channel identifier from theseplurality of channel identifiers).

[0159] It is also possible to define a unique channel identifier for theAV/C protocol with respect to all terminals in advance. It is alsopossible to define a unique channel identifier for the AV/C command withrespect to all terminals in advance, while defining a unique channelidentifier for the AV/C response with respect to all terminals inadvance.

[0160] Also, the above described embodiments are directed to theexemplary case where the radio terminal of an AV data receiving sidetransmits a signaling request (at a time of issuing a playback requestof the AV/C protocol, for example) and in response to this the radioterminal of an AV data transmitting side transmits a signaling response,but the case where the radio terminal of an AV data transmitting sidetransmits a signaling request (at a time of issuing a reception requestof the AV/C protocol, for example) and in response to this the radioterminal of an AV data receiving side transmits a signaling response isalso possible similarly.

[0161] Also, the above described embodiments are directed to theexemplary case of using the Bluetooth, but the present invention is alsoapplicable to radio terminals of any other radio LAN system for carryingout data transfer after establishing a logical connection between radioterminals prior to data transfer between radio terminals.

[0162] Also, the above described embodiments are directed to theexemplary case of using the AV/C protocol as the AV control protocol forthe AV data transfer, but the present invention is also applicable tothe case of using any other AV control protocol.

[0163] Also, the present invention is equally applicable to a homenetwork and a network provided in an office or any other environment.

[0164] It is to be noted that each radio terminal in the above describedembodiments can be realized by a radio terminal device 50 as shown inFIG. 15, for use in a radio system for carrying out data transfer afterestablishing a logical connection between radio terminals or gatewaysprior to data transfer between radio terminals or gateways.

[0165] This radio terminal device 50 of FIG. 15 comprises: a signalingpacket exchange unit 51 for exchanging signaling packets at a datalinklayer with a correspondent radio terminal or gateway prior to anexchange of data packets on which the information regarding the AVcontrol protocol is loaded, where each signaling packet contains achannel identifier indicating a logical channel that is set up fortransferring the data packets and a protocol identifier indicating theAV control protocol; a memory unit 52 for storing a correspondenceinformation among the protocol identifier, the channel identifier thatis set up for the radio terminal device, and the channel identifier thatis set up for the correspondent radio terminal or gateway, which areobtained through an exchange of the signaling packets; a data packetexchange unit 53 for exchanging the data packets with the correspondentradio terminal or gateway, according to the correspondence information;and a radio terminal processing unit 54 for carrying out the processingof the radio terminal.

[0166] The data packet exchange unit 53 includes a data packettransmission unit 531 for transmitting an outgoing data packet byattaching the channel identifier that is set up for the correspondentradio terminal or gateway and that is obtained by referring to thecorrespondence information; a data packet reception unit 532 forreceiving an incoming data packet from the correspondent radio terminalor gateway; and a data packet processing unit 533 for giving theinformation regarding the AV control protocol as contained in theincoming data packet to the AV control protocol, when the incoming datapacket is judged as a packet regarding the AV control protocol byreferring to the correspondence information according to the channelidentifier as described in the incoming data packet, The AV controlprotocol 541 is provided in the radio terminal processing unit 54.

[0167] It is also to be noted that each radio gateway in the abovedescribed embodiments can be realized by a radio gateway device 60 asshown in FIG. 16, for connecting an IEEE 1394 bus with a radio networkfor carrying out data transfer after establishing a logical connectionbetween radio terminals or gateways prior to data transfer between radioterminals or gateways.

[0168] This radio gateway device 60 of FIG. 16 comprises: a signalingpacket exchange unit 61 for exchanging signaling packets at a datalinklayer with a correspondent radio terminal or gateway on the radionetwork prior to an exchange of data packets on which informationregarding an AV control protocol is loaded, where each signaling packetcontains a channel identifier indicating a logical channel that is setup for transferring the data packets and a protocol identifierindicating the AV control protocol; a memory unit 62 for storing acorrespondence information among the protocol identifier, the channelidentifier that is set up for the radio gateway device, and the channelidentifier that is set up for the correspondent radio terminal orgateway, which are obtained through an exchange of the signalingpackets; a data packet transfer unit 63 for transferring the datapackets from a radio network side to an IEEE 1394 bus side or from theIEEE 1394 bus side to the radio network side, according to thecorrespondence information; and a radio gateway processing unit 64 forcarrying out the processing of the radio gateway.

[0169] The data packet transfer unit 63 includes a radio network sidedata packet transmission unit 631 for transmitting an outgoing datapacket on which the command of the AV control protocol or the responseof the AV control protocol is loaded, to the IEEE 1394 side, bydescribing a register offset value indicating the command of the AVcontrol protocol or a register offset value indicating the response ofthe AV control protocol in the outgoing data packet; a radio networkside data packet reception unit 632 for receiving an incoming datapacket to be transferred to the IEEE 1394 side from the radio networkside; a data packet processing unit 633 for checking whether a messagetype of the incoming data packet is a command of the AV control protocolor a response of the AV control protocol when the channel identifierthat is set up for the radio gateway device is described in the incomingdata packet; an IEEE 1394 side data packet reception unit 634 forreceiving an incoming data packet to be transferred to the radio networkside from the IEEE 1394 side; and an IEEE 1394 side data packettransmission unit 635 for transmitting an outgoing data packet on whicha command of the AV control protocol or a response of the AV controlprotocol is loaded, to the radio network side, by describing the channelidentifier that is set up for the correspondent radio terminal orgateway in the outgoing data packet, when a register offset valueindicating the command of the AV control protocol or a register offsetvalue indicating the response of the AV control protocol is described inthe incoming data packet.

[0170] The AV control protocol 641 is provided in the radio gatewayprocessing unit 64.

[0171] It is also to be noted that the above described embodimentsaccording to the present invention may be conveniently implemented usinga conventional general purpose digital computer programmed according tothe teachings of the present specification, as will be apparent to thoseskilled in the computer art. Appropriate software coding can readily beprepared by skilled programmers based on the teachings of the presentdisclosure, as will be apparent to those skilled in the software art.

[0172] In particular, the radio terminal and the radio gateway of eachof the above described embodiments can be conveniently implemented in aform of a software package.

[0173] Such a software package can be a computer program product whichemploys a storage medium including stored computer code which is used toprogram a computer to perform the disclosed function and process of thepresent invention. The storage medium may include, but is not limitedto, any type of conventional floppy disks, optical disks, CD-ROMs,magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnetic or opticalcards, or any other suitable media for storing electronic instructions.

[0174] It is also to be noted that, besides those already mentionedabove, many modifications and variations of the above embodiments may bemade without departing from the novel and advantageous features of thepresent invention. Accordingly, all such modifications and variationsare intended to be included within the scope of the appended claims.

What is claimed is:
 1. An information transfer method for transferringinformation regarding an AV control protocol in a radio system forcarrying out data transfer after establishing a logical connectionbetween radio terminals or gateways prior to data transfer between radioterminals or gateways, the method comprising the steps of: exchangingsignaling packets for signaling at a datalink layer between the radioterminals or gateways prior to an exchange of data packets on which theinformation regarding the AV control protocol is loaded, each signalingpacket containing a channel identifier indicating a logical channel thatis set up for transferring the data packets and a protocol identifierindicating the AV control protocol, such that a signaling packettransmitted from each radio terminal or gateway indicates a channelidentifier that is set up for the each radio terminal or gateway and asignaling packet received from a correspondent radio terminal or gatewayindicates a channel identifier that is set up for the correspondentradio terminal or gateway; storing at the each radio terminal or gatewaya correspondence information obtained through an exchange of thesignaling packets, the correspondence information indicating acorrespondence among the protocol identifier, the channel identifierthat is set up for the each radio terminal or gateway, and the channelidentifier that is set up for the correspondent radio terminal orgateway; and transferring the data packets between the radio terminalsor gateways, according to the correspondence information.
 2. The methodof claim 1 , wherein the transferring step transmits an outgoing datapacket by attaching the channel identifier that is set up for thecorrespondent radio terminal or gateway and that is obtained byreferring to the correspondence information.
 3. The method of claim 1 ,wherein the transferring step receives an incoming data packet from thecorrespondent radio terminal or gateway, and gives the informationregarding the AV control protocol as contained in the incoming datapacket to the AV control protocol, when the incoming data packet isjudged as a packet regarding the AV control protocol by referring to thecorrespondence information according to the channel identifier asdescribed in the incoming data packet,
 4. The method of claim 1 ,wherein the exchanging step uses the channel identifier indicating thelogical channel that is set up at a time of the signaling.
 5. The methodof claim 1 , wherein the exchanging step uses the channel identifierindicating the logical channel that is set up prior to the signaling. 6.The method of claim 1 , wherein the exchanging step uses the channelidentifier indicating the logical channel that is specified with respectto all radio terminals or gateways in advance.
 7. The method of claim 1, wherein values of the protocol identifier are defined separately fordifferent message types in the AV control protocol, and the exchangingstep carries out the signaling for each message type of the AV controlprotocol, using different channel identifiers for different messagetypes in the AV control protocol.
 8. An information transfer method fortransferring information regarding an AV control protocol at a radiogateway connecting an IEEE 1394 bus with a radio network for carryingout data transfer after establishing a logical connection between radioterminals or gateways prior to data transfer between radio terminals orgateways, the method comprising the steps of: exchanging signalingpackets for signaling at a datalink layer with a correspondent radioterminal or gateway on the radio network prior to an exchange of datapackets on which the information regarding the AV control protocol isloaded, each signaling packet containing a channel identifier indicatinga logical channel that is set up for transferring the data packets and aprotocol identifier indicating the AV control protocol, such that asignaling packet transmitted from the radio gateway indicates a channelidentifier that is set up for the radio gateway and a signaling packetreceived from the correspondent radio terminal or gateway indicates achannel identifier that is set up for the correspondent radio terminalor gateway; storing a correspondence information obtained through anexchange of the signaling packets, the correspondence informationindicating a correspondence among the protocol identifier, the channelidentifier that is set up for the radio gateway, and the channelidentifier that is set up for the correspondent radio terminal orgateway; and transferring the data packets from a radio network side toan IEEE 1394 bus side or from the IEEE 1394 bus side to the radionetwork side, according to the correspondence information.
 9. The methodof claim 8 , wherein the transferring step includes the steps of:receiving an incoming data packet to be transferred to the IEEE 1394side from the radio network side; checking whether a message type of theincoming data packet is a command of the AV control protocol or aresponse of the AV control protocol when the channel identifier that isset up for the radio gateway is described in the incoming data packet;and transmitting an outgoing data packet on which the command of the AVcontrol protocol or the response of the AV control protocol is loaded,to the IEEE 1394 side, by describing a register offset value indicatingthe command of the AV control protocol or a register offset valueindicating the response of the AV control protocol in the outgoing datapacket.
 10. The method of claim 8 , wherein the transferring stepincludes the steps of: receiving an incoming data packet to betransferred to the radio network side from the IEEE 1394 side; andtransmitting an outgoing data packet on which a command of the AVcontrol protocol or a response of the AV control protocol is loaded, tothe radio network side, by describing the channel identifier that is setup for the correspondent radio terminal or gateway in the outgoing datapacket, when a register offset value indicating the command of the AVcontrol protocol or a register offset value indicating the response ofthe AV control protocol is described in the incoming data packet. 11.The method of claim 8 , wherein the exchanging step uses the channelidentifier indicating the logical channel that is set up at a time ofthe signaling.
 12. The method of claim 8 , wherein the exchanging stepuses the channel identifier indicating the logical channel that is setup prior to the signaling.
 13. The method of claim 8 , wherein theexchanging step uses the channel identifier indicating the logicalchannel that is specified with respect to all radio terminals orgateways in advance.
 14. The method of claim 8 , wherein values of theprotocol identifier are defined separately for different message typesin the AV control protocol, and the exchanging step carries out thesignaling for each message type of the AV control protocol, usingdifferent channel identifiers for different message types in the AVcontrol protocol.
 15. The method of claim 8 , wherein the transferringstep transmits data packets on which one set of the command of the AVcontrol protocol and the response of the AV control protocol are loadedby attaching an identical transaction identifier to the data packets.16. A radio terminal device in a radio system for carrying out datatransfer after establishing a logical connection between radio terminalsor gateways prior to data transfer between radio terminals or gateways,the radio terminal device comprising: a signaling packet exchange unitconfigured to exchange signaling packets for signaling at a datalinklayer with a correspondent radio terminal or gateway prior to anexchange of data packets on which the information regarding the AVcontrol protocol is loaded, each signaling packet containing a channelidentifier indicating a logical channel that is set up for transferringthe data packets and a protocol identifier indicating the AV controlprotocol, such that a signaling packet transmitted from the radioterminal device indicates a channel identifier that is set up for theradio terminal device and a signaling packet received from thecorrespondent radio terminal or gateway indicates a channel identifierthat is set up for the correspondent radio terminal or gateway; a memoryunit configured to store a correspondence information obtained throughan exchange of the signaling packets, the correspondence informationindicating a correspondence among the protocol identifier, the channelidentifier that is set up for the radio terminal device, and the channelidentifier that is set up for the correspondent radio terminal orgateway; and a data packet exchange unit configured to exchange the datapackets with the correspondent radio terminal or gateway, according tothe correspondence information.
 17. The radio terminal device of claim16 , wherein the data packet exchange unit includes: a data packettransmission unit configured to transmit an outgoing data packet byattaching the channel identifier that is set up for the correspondentradio terminal or gateway and that is obtained by referring to thecorrespondence information.
 18. The radio terminal device of claim 16 ,wherein the data packet exchange unit includes: a data packet receptionunit configured to receive an incoming data packet from thecorrespondent radio terminal or gateway; and a data packet processingunit configured to give the information regarding the AV controlprotocol as contained in the incoming data packet to the AV controlprotocol, when the incoming data packet is judged as a packet regardingthe AV control protocol by referring to the correspondence informationaccording to the channel identifier as described in the incoming datapacket.
 19. The radio terminal device of claim 16 , wherein thesignaling packet exchange unit uses the channel identifier indicatingthe logical channel that is set up at a time of the signaling.
 20. Theradio terminal device of claim 16 , wherein the signaling packetexchange unit uses the channel identifier indicating the logical channelthat is set up prior to the signaling.
 21. The radio terminal device ofclaim 16 , wherein the signaling packet exchange unit uses the channelidentifier indicating the logical channel that is specified with respectto all radio terminals or gateways in advance.
 22. The radio terminaldevice of claim 16 , wherein values of the protocol identifier aredefined separately for different message types in the AV controlprotocol, and the signaling packet exchange unit carries out thesignaling for each message type of the AV control protocol, usingdifferent channel identifiers for different message types in the AVcontrol protocol.
 23. A radio gateway device connecting an IEEE 1394 buswith a radio network for carrying out data transfer after establishing alogical connection between radio terminals or gateways prior to datatransfer between radio terminals or gateways, the radio gateway devicecomprising: a signaling packet exchange unit configured to exchangesignaling packets for signaling at a datalink layer with a correspondentradio terminal or gateway on the radio network prior to an exchange ofdata packets on which information regarding an AV control protocol isloaded, each signaling packet containing a channel identifier indicatinga logical channel that is set up for transferring the data packets and aprotocol identifier indicating the AV control protocol, such that asignaling packet transmitted from the radio gateway device indicates achannel identifier that is set up for the radio gateway device and asignaling packet received from the correspondent radio terminal orgateway indicates a channel identifier that is set up for thecorrespondent radio terminal or gateway; a memory unit configured tostore a correspondence information obtained through an exchange of thesignaling packets, the correspondence information indicating acorrespondence among the protocol identifier, the channel identifierthat is set up for the radio gateway device, and the channel identifierthat is set up for the correspondent radio terminal or gateway; and adata packet transfer unit configured to transfer the data packets from aradio network side to an IEEE 1394 bus side or from the IEEE 1394 busside to the radio network side, according to the correspondenceinformation.
 24. The radio gateway device of claim 23 , wherein the datapacket transfer unit includes: a radio network side data packetreception unit configured to receive an incoming data packet to betransferred to the IEEE 1394 side from the radio network side; a datapacket processing unit configured to check whether a message type of theincoming data packet is a command of the AV control protocol or aresponse of the AV control protocol when the channel identifier that isset up for the radio gateway device is described in the incoming datapacket; and a radio network side data packet transmission unitconfigured to transmit an outgoing data packet on which the command ofthe AV control protocol or the response of the AV control protocol isloaded, to the IEEE 1394 side, by describing a register offset valueindicating the command of the AV control protocol or a register offsetvalue indicating the response of the AV control protocol in the outgoingdata packet.
 25. The radio gateway device of claim 23 , wherein the datapacket transfer unit includes: an IEEE 1394 side data packet receptionunit configured to receive an incoming data packet to be transferred tothe radio network side from the IEEE 1394 side; and an IEEE 1394 sidedata packet transmission unit configured to transmit an outgoing datapacket on which a command of the AV control protocol or a response ofthe AV control protocol is loaded, to the radio network side, bydescribing the channel identifier that is set up for the correspondentradio terminal or gateway in the outgoing data packet, when a registeroffset value indicating the command of the AV control protocol or aregister offset value indicating the response of the AV control protocolis described in the incoming data packet.
 26. The radio gateway deviceof claim 23 , wherein the signaling packet exchange unit uses thechannel identifier indicating the logical channel that is set up at atime of the signaling.
 27. The radio gateway device of claim 23 ,wherein the signaling packet exchange unit uses the channel identifierindicating the logical channel that is set up prior to the signaling.28. The radio gateway device of claim 23 , wherein the signaling packetexchange unit uses the channel identifier indicating the logical channelthat is specified with respect to all radio terminals or gateways inadvance.
 29. The radio gateway device of claim 23 , wherein values ofthe protocol identifier are defined separately for different messagetypes in the AV control protocol, and the signaling packet exchange unitcarries out the signaling for each message type of the AV controlprotocol, using different channel identifiers for different messagetypes in the AV control protocol.
 30. The radio gateway device of claim23 , wherein the data packet transfer unit transmits data packets onwhich one set of the command of the AV control protocol and the responseof the AV control protocol are loaded by attaching an identicaltransaction identifier to the data packets.
 31. A computer usable mediumhaving computer readable program codes embodied therein for causing acomputer to function as a radio terminal device in a radio system forcarrying out data transfer after establishing a logical connectionbetween radio terminals or gateways prior to data transfer between radioterminals or gateways, the computer readable program codes include: afirst computer readable program code for causing said computer toexchange signaling packets for signaling at a datalink layer with acorrespondent radio terminal or gateway prior to an exchange of datapackets on which the information regarding the AV control protocol isloaded, each signaling packet containing a channel identifier indicatinga logical channel that is set up for transferring the data packets and aprotocol identifier indicating the AV control protocol, such that asignaling packet transmitted from the radio terminal device indicates achannel identifier that is set up for the radio terminal device and asignaling packet received from the correspondent radio terminal orgateway indicates a channel identifier that is set up for thecorrespondent radio terminal or gateway; a second computer readableprogram code for causing said computer to store a correspondenceinformation obtained through an exchange of the signaling packets, thecorrespondence information indicating a correspondence among theprotocol identifier, the channel identifier that is set up for the radioterminal device, and the channel identifier that is set up for thecorrespondent radio terminal or gateway; and a third computer readableprogram code for causing said computer to exchange the data packets withthe correspondent radio terminal or gateway, according to thecorrespondence information.
 32. A computer usable medium having computerreadable program codes embodied therein for causing a computer tofunction as a radio gateway device connecting an IEEE 1394 bus with aradio network for carrying out data transfer after establishing alogical connection between radio terminals or gateways prior to datatransfer between radio terminals or gateways, the computer readableprogram codes include: a first computer readable program code forcausing said computer to exchange signaling packets at a datalink layerwith a correspondent radio terminal or gateway on the radio networkprior to an exchange of data packets on which information regarding anAV control protocol is loaded, each signaling packet containing achannel identifier indicating a logical channel that is set up fortransferring the data packets and a protocol identifier indicating theAV control protocol, such that a signaling packet transmitted from theradio gateway device indicates a channel identifier that is set up forthe radio gateway device and a signaling packet received from thecorrespondent radio terminal or gateway indicates a channel identifierthat is set up for the correspondent radio terminal or gateway; a secondcomputer readable program code for causing said computer to store acorrespondence information obtained through an exchange of the signalingpackets, the correspondence information indicating a correspondenceamong the protocol identifier, the channel identifier that is set up forthe radio gateway device, and the channel identifier that is set up forthe correspondent radio terminal or gateway; and a third computerreadable program code for causing said computer to transfer the datapackets from a radio network side to an IEEE 1394 bus side or from theIEEE 1394 bus side to the radio network side, according to thecorrespondence information.